1. Field of the Invention
The present invention relates to a color three-dimensional image display device capable of displaying three-dimensional images, a portable terminal device mounting the three-dimensional image display device, and a display panel and fly eye lens to be built in the three-dimensional image display device, and more specifically relates to a three-dimensional image display device, portable terminal device, display panel, and fly eye lens, which are capable of stereoscopic viewing even in the event that the three-dimensional image display device is disposed not only in one direction alone but also in another direction orthogonal to this one direction.
Examples of applications to which the present invention is applied include portable terminal devices such as handheld phones, PDAs, game devices, digital cameras, and digital video cameras.
2. Description of the Related Art
Conventionally, studies of a display device capable of displaying three-dimensional images have been made. The Greek Mathematician Euclid, in 280 BC, observed that depth perception is to perceive the same object with the left and right eyes, each simultaneously looking at different views of that one object in different directions (for example, see “Three-dimensional Display” (Chihiro Masuda, pub. Sangyo Tosho Publishing Co. Ltd.)). That is to say, three-dimensional image display devices need to function in showing images with parallax independently to each eye of an observer. As for a method for realizing this function specifically, while various kinds of methods for displaying three-dimensional images have been studied for a long time, these methods can be roughly basically categorized into a method using glasses and a method not using glasses. Among these, examples of the method using glasses include the anaglyph method using color difference and the polarization glasses method using polarization. However, since these methods cannot avoid being troublesome by requiring the wearing of glasses, in recent years, methods wherein wearing glasses is not necessary have been intensively studied. Examples of method not requiring wearing of glasses include the lenticular lens method and parallax barrier method.
Firstly, a description will be made regarding the lenticular lens method. As described in the aforementioned “Three-dimensional Display” (Chihiro Masuda, pub. Sangyo Tosho Publishing Co. Ltd.) for example, the lenticular lens method has been invented by Ives and others around 1910. FIG. 1 is a perspective view illustrating a lenticular lens, and FIG. 2 is an optical model diagram illustrating a conventional three-dimensional image display method using a lenticular lens. As illustrated in FIG. 1, a lenticular lens 121 has one side with a flat surface, and the other side on which a plurality of convex portions of rounded ridges extending in one direction (cylindrical lens 122) are formed such that the longitudinal directions thereof are parallel to each other.
Subsequently, as illustrated in FIG. 2, with a three-dimensional image display device using the lenticular lens method, a lenticular lens 121, display panel 106, and light source 108 are disposed in that order from the observer side, and the pixels of the display panel 106 are disposed on the focus surface of the lenticular lens 121. On the display panel 106, pixels 123 for displaying an image for the right eye 141 and pixels 124 for displaying an image for the left eye 142 are alternatively arrayed. At this time, a set made up of the pixels 123 and 124 adjacent to each other corresponds to each cylindrical lens (convex portion) of the lenticular lenses 121. Thus, the light emitted from the light source 108 passes through each pixel, and is distributed in the direction toward the left eye and in the direction toward the right eye by means of the cylindrical lens 122 of the lenticular lens 121. This enables the left and right eyes to recognize a different image mutually, thereby enabling the observer to recognize a three-dimensional image. As described above, since this method is displaying a left-eye image on the left eye and a right-eye image on the right eye, enabling an observer to recognize a three-dimensional image is called a dual-viewpoint method for forming two viewpoints.
Next, the size of each component of a three-dimensional image display device will be described including a normal lenticular lens and display panel. FIG. 3 is a diagram illustrating an optical model of a dual-viewpoint three-dimensional image display device using the normal lenticular lens method, and FIG. 4 is a diagram illustrating a stereoscopic vision region of this dual-viewpoint three-dimensional image display device. As illustrated in FIG. 3, let us say that the distance between the apex of the lenticular lens 121 and the pixel of the display panel 106 is H, the index of refraction of the lenticular lens 121 is n, the focal distance is f, and the array cycle of lens elements, i.e., the lens pitch, is L. The display pixels of the display panel 106 are disposed as one set of each left-eye pixel 124 and each right-eye pixel 123. If the pitch of this pixel is P, the array pitch of the display pixels is accordingly made up of each left-eye pixel 124 and each right-eye pixel 123 is 2 P. One cylindrical lens 122 is disposed corresponding to the display pixels made up of the two pixels of each left-eye pixel 124 and each right-eye pixel 123.
Also, let us say that the distance between the lenticular lens 121 and the observer is an optimal observation distance OD, and the magnifying projection width of one pixel in this distance OD, i.e., the widths of the projection images of the left-eye pixel 124 and right-eye pixel 123 on an imaginary flat surface distanced from a lens by the distance OD and parallel to the lens are each e. Further, let us say that the distance between the center of the cylindrical lens 122 positioned at the center of the lenticular lens 121 and the center of the cylindrical lens 122 disposed on the end of the lenticular lens 121 in a horizontal direction 112 is WL, and the distance between the center of the display pixels made up of the left-eye pixel 124 and right-eye pixel 123 positioned on the center of the display panel 106 and the center of the display pixels positioned on the end of the display panel 106 in the horizontal direction 112 is WP. Further, let us say that the incident angle and exiting angle of light in the cylindrical lens 122 positioned on the center of the lenticular lens 121 are α and β respectively, and the incident angle and exiting angle of light in the convex portions 122 positioned on the end of the lenticular lens 121 in the horizontal direction 112 are γ and δ respectively. Further, let us say that the difference between the distance WL and the distance WP is C, and the number of pixels included in the distance WP is 2 m.
Since the array pitch L of the cylindrical lens 122 and the array pitch P of the pixels are mutually correlated, coordinating with one determines the other. However, normally, a lenticular lens is often designed by coordinating with a display panel, so the array pitch P of the pixels is handled as a constant. In addition, selecting the material of the lenticular lens 121 determines the index of refraction n. On the other hand, with regard to the observation distance OD between the lens and the observer, and the pixel magnifying projection width e at the observation distance OD, desired values are set. The distance H between the apex of the lens and the pixels and the lens pitch L will be determined using the aforementioned values. Due to Snell's law and geometrical relations, the following Expressions 1 through 6 are established. The following Expressions 7 through 9 are also established.n×sin a=sin b  (Expression 1)OD×tan b=e  (Expression 2)H×tan a=P  (Expression 3)n×sin g=sin d  (Expression 4)H×tan g=C  (Expression 5)OD×tan d=WL  (Expression 6)WP−WL=C  (Expression 7)WP=2×m×P  (Expression 8)WL=m×L  (Expression 9)
From the aforementioned Expressions 1 through 3, the following Expressions 10 through 12 are established respectively.β=arc tan(e/OD)  (Expression 10)α=arc sin(1/n×sin β)  (Expression 11)H=P/tan α  (Expression 12)
Also, the following Expression 13 is established from the above Expressions 6 and 9. Moreover, the following Expression 14 is established from the aforementioned Expressions 8 and 9. Furthermore, the following Expression 15 is established from the aforementioned Expression 5.δ=arc tan(mL/OD)  (Expression 13)C=2×m×P−m×L  (Expression 14)γ=arc tan(C/H)  (Expression 15)
Since the distance H between the apex of the lenticular lens and the pixels is usually set so as to be identical to the focal distance f of the lenticular lens, the following Expression 16 is established. If we say that the curvature radius of the lenticular lens is r, the curvature radius is obtained from the following Expression 17.f=H  (Expression 16)r=H×(n−1)/n  (Expression 17)
As illustrated in FIG. 4, let us say that a region where light reaches from all of the right-eye pixels 123 is a right-eye region 171, and a region where light reaches from all of the left-eye pixels 124 is a left-eye region 172. The observer can recognize a three-dimensional image by positioning the right eye 141 to the right-eye region 171, and the left eye 142 to the left-eye region 172. However, since the interpupillary distance of the observer is constant, the right eye 141 and left eye 142 cannot be positioned at an arbitrary position of the right-eye region 171 and left-eye region 172 respectively, and accordingly, the positions are restricted to a region where the interpupillary distance can be kept to a constant. In other words, only in the case wherein the midpoint of the right eye 141 and left eye 142 is positioned at a stereoscopic vision region 107, can stereoscopic viewing be obtained. Since a length along the horizontal direction 112 in the stereoscopic vision region 107 becomes the longest at the position where a distance from the display panel 106 is identical to the optimal observation distance OD, tolerance in deviation of the observer's position in the horizontal direction 112 reaches the maximal value. Accordingly, the position where the distance from the display panel 106 is the optimal observation distance OD is the most ideal observation position.
As described later, while the parallax barrier method is a method for hiding unnecessary light by a barrier, the lenticular lens method is a method for changing the direction where light advances, and accordingly, employing the lenticular lens does not reduce the brightness of a display screen in principle. Accordingly, the lenticular lens method is most likely to be applied to portable equipment and so forth in which high-luminance display and low consumption power performance are regarded as important factors.
A development example of three-dimensional image display devices using the lenticular lens method is described in Nikkei Electronics No. 838, Jan. 6, 2003 pp 26-27. A 7-inch liquid crystal panel making up a three-dimensional image display device includes 800×480 display dots. Three-dimensional image display and flat image display can be switched by changing the distance between the lenticular lens and the liquid crystal display panel by 0.6 mm. The number of lateral viewpoints is five, and accordingly, five different images can be viewed by changing the view angle in the horizontal direction. On the other hand, the number of vertical viewpoints is one, and accordingly, the image does not change even if the view angle is changed in the vertical direction.
Next, the parallax barrier method will be described. The parallax barrier method was conceived by Berthier in 1896, and demonstrated by Ives in 1903. FIG. 5 is an optical model diagram illustrating a conventional three-dimensional image display method using a parallax barrier. As illustrated in FIG. 5, a parallax barrier 105 is a barrier (shielding plate) on which numerous narrow slits 105a are formed. The display panel 106 is disposed near one surface of this parallax barrier 105. On the display panel 106, the right-eye pixels 123 and left-eye pixels 124 are arrayed in the direction orthogonal to the longitudinal direction of the slits. On the other hand, the light source 108 is disposed near the other surface of the parallax barrier 105, i.e., on the opposite side of the display panel 106.
The light, which is emitted from the light source 108, and passes through the slit 105a of the parallax barrier 105 and the right-eye pixel 123, is the optical flux 181. In the same way, the light, which is emitted from the light source 108, passes through the slit 105a and the left-eye pixel 124, is optical flux 182. At this time, the position where the observer can recognize a three-dimensional image is determined by means of the positional relation between the parallax barrier 105 and the pixels. In other words, the right eye 141 of an observer 104 needs to be within the regions of all of the optical flux 181 corresponding to the a plurality of right-eye pixels 123, and also the left eye 142 of the observer needs to be within the transmissive regions of all of the optical flux 182. This is the case wherein a midpoint 143 of the right eye 141 and left eye 142 of the observer is positioned within the stereoscopic vision region 107 of a square illustrated in FIG. 5.
Of the line segments extending in the array direction of the right-eye pixel 123 and left-eye pixel 124 in the stereoscopic vision region 107, the segment passing through a diagonal intersecting point 107a in the stereoscopic vision region 107 is the longest line segment. Accordingly, when the midpoint 143 is positioned at the intersecting point 107a, tolerance in a case wherein the position of the observer deviates in the horizontal direction reaches the maximal value, so this position is the most preferable as an observation position. Accordingly, with this three-dimensional image display method, it is recommended for observers to perform observation at the optimal observation distance OD, i.e., distance between the intersecting point 107a and the display panel 106. Note that an imaginary flat surface wherein the distance from the display panel 106 in the stereoscopic vision region 107 is the optimal observation distance OD is called as an optimal observation surface 107b. Thus, the light from the right-eye pixel 123 and left-eye pixel 124 reaches the right eye 141 and left eye 142 of the observer respectively. Accordingly, the observer can recognize an image displayed on the display panel 106 as a three-dimensional image.
Next, a three-dimensional image display device is described wherein a parallax barrier on which slits are formed is disposed on the front surface of a display panel, more specifically, regarding each component size thereof in detail. FIG. 6 is a diagram illustrating an optical model of a conventional dual-viewpoint three-dimensional image display device having a slit-shaped parallax barrier on the observer side of a display panel. Note that the slit width of the parallax barrier is minute, so it can be ignored for the sake of simplifying explanation. As illustrated in FIG. 6, let us say that the array pitch of the slits 105a of the parallax barrier 105 is L, the distance between the display panel 106 and the parallax barrier 105 is H, and also the array pitch of the pixels is P. As described above, with the display panel 106, since two pixels, i.e., each right-eye pixel 123 and each left-eye pixel 124 are disposed as a pixel set on the display panel 106, the array pitch of the pixel set is 2 P. Since the array pitch L of the slits 105a and the array pitch P of the pixel set are mutually correlated, coordinating with one determines the other, however, normally, a parallax barrier is often designed by coordinating with a display panel, so the array pitch P of the pixel set is handled as a constant.
Also, let us say that a region where light reaches from all of the right-eye pixels 123 is the right-eye region 171, and a region where light reaches from all of the left-eye pixels 124 is the left-eye region 172. The observer can recognize a three-dimensional image by positioning the right eye 141 to the right-eye region 171, and the left eye 142 to the left-eye region 172. However, since the interpupillary distance of the observer is constant, the right eye 141 and left eye 142 cannot be positioned to an arbitrary position of the right-eye region 171 and left-eye region 172 respectively, and accordingly, the positions are restricted to a region where the interpupillary distance can be kept constant. In other words, only in the case wherein the midpoint 143 of the right eye 141 and left eye 142 is positioned at the stereoscopic vision region 107, stereoscopic viewing can be obtained. Since a length along the horizontal direction 112 at the stereoscopic vision region 107 is the longest at the position where a distance from the display panel 106 is identical to the optimal observation distance OD, tolerance in a case wherein the position of the observer deviates toward the horizontal direction 112 reaches the maximal value. Accordingly, the position where the distance from the display panel 106 is the optimal observation distance OD is the most ideal observation position. Also, let us say that an imaginary flat surface wherein the distance from the display panel 106 in the stereoscopic vision region 107 is the optimal observation distance OD is the optimal observation surface 107b, and the magnifying projection width of one pixel in the optimal observation surface 107b is e.
Next, the distance H between the parallax barrier 105 and the display pixels of the display panel 106 will be determined using the aforementioned values. Due to geometrical relations as illustrated in FIG. 6, the following Expressions 18 is established, and thus, the distance H is obtained as illustrated in the following Expression 19.P:H=e:(OD−H)  (Expression 18)H=OD×P/(P+e)  (Expression 19)
Further, if we say that the distance between the center of the pixel set positioned at the center of the display panel 106 in the horizontal direction 112 and the center of the pixel set positioned on the end in the horizontal direction 112 is WP, and the distance between the centers of the slits 105a corresponding to these pixel sets respectively is WL, the difference C between the distance WP and distance WL is obtained by the following Expression 20. Also, if we say that the number of pixels included in the distance WP on the display panel 106 is 2 m, the following Expression 21 is established. Further, since the following Expression 22 is established due to geometrical relations, the pitch L of the slits 105a of the parallax barrier 105 is obtained by the following Expression 23.WP−WL=C  (Expression 20)WP=2×m×Pm, WL=m×L  (Expression 21)WP:OD=WL:(OD−H)  (Expression 22)L=2×P×(OD−H)/OD  (Expression 23)
Next, a three-dimensional image display device is described wherein a parallax barrier is disposed on the rear surface of the display panel, more specifically, regarding each component size thereof in detail. FIG. 7 is a diagram illustrating an optical model of a conventional dual-viewpoint three-dimensional image display device having a slit-shaped parallax barrier on the rear surface of a display panel. Note that the slit width of the parallax barrier is minute, so this can be ignored for the sake of simplifying explanation. As with the aforementioned case wherein the parallax barrier is disposed on the front surface of the display panel, let us say that the array pitch of the slits 105a of the parallax barrier 105 is L, the distance between the display panel 106 and the parallax barrier 105 is H, and also the array pitch of the display pixels is P. As described above, with the display panel 106, since two pixels, i.e., each right-eye pixel 123 and each left-eye pixel 124 are disposed as a pixel set on the display panel 106, the array pitch of the pixel set is 2 P . Since the array pitch L of the slits 105a and the array pitch P of the pixel set are mutually correlated, coordinating with one determines the other, however, normally, a parallax barrier is often designed by coordinating with a display panel, so the array pitch P of the pixel set is handled as a constant.
Also, let us say that a region where light reaches from all of the right-eye pixels 123 is the right-eye region 171, and a region where light reaches from all of the left-eye pixels 124 is the left-eye region 172. The observer can recognize a three-dimensional image by positioning the right eye 141 to the right-eye region 171, and the left eye 142 to the left-eye region 172. However, since the interpupillary distance of the observer is constant, the right eye 141 and left eye 142 cannot be positioned to an arbitrary position of the right-eye region 171 and left-eye region 172 respectively, and accordingly, the positions are restricted to a region where the interpupillary distance can be kept constant. In other words, only in the case wherein the midpoint 143 of the right eye 141 and left eye 142 is positioned at the stereoscopic vision region 107, stereoscopic viewing can be obtained. Since the length along the horizontal direction 112 at the stereoscopic vision region 107 is the longest at the position where a distance from the display panel 106 is identical to the optimal observation distance OD, tolerance in a case wherein the position of the observer deviates toward the horizontal direction 112 reaches the maximal value. Accordingly, the position where the distance from the display panel 106 is the optimal observation distance OD is the most ideal observation position. Also, let us say that an imaginary flat surface wherein the distance from the display panel 106 in the stereoscopic vision region 107 is the optimal observation distance OD is the optimal observation surface 107b, and the magnifying projection width of one pixel in the optimal observation surface 107b is e.
Next, the distance H between the parallax barrier 105 and the pixels of the display panel 106 will be determined using the aforementioned values. Due to geometrical relations as illustrated in FIG. 7, the following Expressions 24 is established, and thus, the distance H is obtained as illustrated in the following Expression 25.P:H=e:(OD+H)  (Expression 24)H=OD×P/(e−P)  (Expression 25)
Further, if we say that the distance between the center of the pixel set positioned at the center of the display panel 106 in the horizontal direction 112 and the center of the pixel set positioned on the end in the horizontal direction 112 is WP, and the distance between the centers of the slits 105a corresponding to these pixel sets respectively is WL, the difference C between the distance WP and distance WL is obtained by the following Expression 26. Also, if we say that the number of pixels included in the distance WP on the display panel 106 is 2 m, the following Expression 27 and Expression 28 are established. Further, since the following Expression 29 is established due to geometrical relations, the pitch L of the slits 105a of the parallax barrier 105 is obtained by the following Expression 30.WL−WP=C  (Expression 26)WP=2×m×P  (Expression 27)WL=m×L  (Expression 28)WP:OD=WL:(OD+H)  (Expression 29)L=2×P×(OD+H)/OD  (Expression 30)
Since the parallax barrier method originally had the parallax barrier disposed between the pixel and the eye, this has led to a problem wherein the parallax barrier is conspicuous and visibility is poor. However, with realization of liquid crystal display panels, an arrangement has been made wherein the parallax barrier 105 can be disposed on the rear side of the display panel 106 as illustrated in FIG. 5, thereby improving visibility. Thus, three-dimensional image display devices using the parallax barrier method are now being studied intensively.
An example of actual production using the parallax barrier method in reality is described within Table 1 of the aforementioned Nikkei Electronics No. 838, Jan. 6, 2003 pp 26-27. This is a portable phone mounting a liquid crystal panel corresponding to 3D, wherein the liquid crystal panel making up a three-dimensional image display device includes 176×220 display dots in diagonal 2.2-inch size. In addition, a liquid crystal panel serving as a switch for turning on/off the effects of a parallax barrier is provided, whereby three-dimensional image display and flat image display can be switched and displayed. As described above, two images of a left-eye image and right-eye image are displayed at the time of displaying a three-dimensional image. In other words, this is a dual-viewpoint three-dimensional image display device.
Meanwhile, attempts for improving stereoscopic sensation have been performed using images more than two images. For example, as described above, a pair of a left-eye image and right-eye image is displayed not only in the horizontal direction but also in the vertical direction. The shape of the slits of a parallax barrier is a pinhole shape. Thus, in the event that the position of the observer moves in the vertical direction, different three-dimensional images can be recognized. A pair of the images disposed in the vertical direction are images wherein a substance to be displayed is observed in the vertical direction. Thus, the observer can obtain stereoscopic sensation in the vertical direction by changing his/her position in the vertical direction, resulting in improving stereoscopic sensation.
A development example of three-dimensional image display devices for displaying an image two-dimensionally in the vertical direction is described in “3D Display” (Optical and electro-optical engineering contact, Vol. 41, No. 3, Mar. 20, 2003 pp. 21-32. This is a multi-viewpoint three-dimensional image display device using 7 viewpoints in the horizontal direction, 4 viewpoints in the vertical direction, for 28 viewpoints in total, and a liquid crystal display device making up the three-dimensional image display device includes QUXGA-W (3840×2400) display dots in a diagonal 22-inch size. Thus, the observer can observe three-dimensional images changing consecutively in the event of changing the observation position not only in the horizontal direction but also in the vertical direction.
However, with the aforementioned conventional three-dimensional image display device, it is assumed that the direction for disposing a display screen is to be set in one direction as to the observer at all times. Accordingly, in the event of changing the direction of the display monitor as to the observer, it is impossible for the observer to recognize a three-dimensional image. For example, upon the aforementioned display device being rotated by 90° in either direction from the normal direction, the observer observes the same image with both eyes, and cannot recognize a three-dimensional image.
To solve this problem, a technique is disclosed in Japanese Unexamined Patent Application Publication No. 06-214323 wherein two lenticular lenses are overlapped such that the longitudinal directions of the lenses are orthogonal to each other, and the focal point of each lens is disposed on the same flat surface, and the light from a plurality of pixels arrayed in matrix fashion is distributed into in the vertical direction and in the horizontal direction of a screen. Thus, Japanese Unexamined Patent Application Publication No. 06-214323 states that even in the event that the direction of the display screen relative to the observer rotates by 90°, such as in a case wherein the observer lies down, the observer can recognize a three-dimensional image.
However, the aforementioned conventional technique includes the following problems. As a result of the efforts made by the present inventor and others studying this technique, with the display device disclosed in Japanese Patent Publication No. Hei 06-214323, in the event of a display of a color image changing the direction for disposing the display device to the observer, it has been proven that three-dimensional display cannot be correctly made in some cases. This phenomenon is described in detail below.
First, a case wherein a lens is employed will be described. In order to observe a three-dimensional image even if the display device is disposed in either the vertical or horizontal direction, with Japanese Unexamined Patent Application Publication No. 06-214323, while two lenticular lenses disposed such that the longitudinal directions of the lenses are orthogonal to each other are employed, a fly eye lens of which lens elements are two-dimensionally arrayed may be employed. FIG. 8 is a perspective view illustrating a fly eye lens 125.
As for a display device to be used in a three-dimensional image display device, a display device employing a striped color, which is currently most common, is used. For the sake of explanation, a first direction and a second direction are defined as follows. That is to say, the first direction is a direction where the same color pixels of each color pixel are consecutively disposed, and the second direction is a direction where each color pixel is alternatively repeatedly disposed. The first direction and the second direction are orthogonal to each other on a display surface. One display unit includes three colors of RGB, and each color pixel is arrayed in a striped shape. Also, the resolution in the first direction and the resolution in the second direction are equally mutually set, and accordingly, each color pixel pitch in the second direction is one third of the pitch in the first direction.
In order to observe a three-dimensional image by disposing left and right pixels not only in the first direction but also in the second direction, a method for disposing one lens element as to two same color pixels arrayed in the second direction and adjacent to each other can be conceived. In this case, since the pixel pitch in the second direction is one third of the pixel pitch in the first direction, the aforementioned Expression 3 is substituted with the following Expression 31.H×tan α′=P/3  (Expression 31)
At this time, the distance H between the lens and the pixel should be the same value as the distance H between the lens and the pixel in the aforementioned first direction for the sake of using one fly eye lens. In the same way, the index of refraction n should be the same. Also, the observation distance OD is preferably unchanged. Thus, Expression 1 is substituted with the following Expression 32. Also, Expression 2 is substituted with the following Expression 33.n×sin α′=sin β′  (Expression 32)OD×tan β′=e′  (Expression 33)
Note that the angles α, β, α′, and β′ are generally small, and are in a range wherein paraxial approximation is established, and accordingly, e′ is generally the same as (e/3), and a pixel magnifying projection width is (e/3). For example, in the event that the pixel magnifying projection width e in the aforementioned first direction is 97.5 mm, the pixel magnifying projection width e/3 in the second direction is 32.5 mm. In other words, left and right images are magnified and projected in 32.5 mm pitch. Consequently, a general observer of which the interpupillary distance is 65 mm can observe only any one of the images, and accordingly, regardless of the display device displaying a three-dimensional image, the observer cannot recognize the three-dimensional image.
Such a problem occurs not only in the lens method but also in the three-dimensional image display device using the parallax barrier method. Description will be made below the phenomenon occurring when the angle of a three-dimensional image display device using the parallax barrier method relative to the observer is rotated by 90° from the normal observation position will be described below.
The conventional three-dimensional image display device illustrated in FIG. 5 is a three-dimensional image display device using a parallax barrier on which slits are formed. When this device is rotated by 90° from the normal position, the observer observes the same image with both eyes, and accordingly, cannot recognize a three-dimensional image. In order to observe a three-dimensional image even if the display device is disposed either vertically or horizontally, there is the need to employ a parallax barrier on which pinhole slits are two-dimensionally arrayed. Note that with the present device, as with the aforementioned device using a fly eye lens, the array of each color is defined in a striped shape, and the first and second directions are defined as the same as the aforementioned definition. Consequently, the pitch of color pixels in the second direction is one third of the pitch in the first direction.
In order to observe a three-dimensional image by disposing left and right images not only in the first direction but also in the second direction, a method for disposing one pinhole as to two color pixels arrayed in the second direction and adjacent to each other can be conceived. In this case, a pixel pitch is one third of the first direction, and accordingly, the aforementioned Expression 19 is substituted with the following Expression 34.e′=((OD−H)/H)×P/3  (Expression 34)
At this time, the distance H between the barrier and the pixel should be the same value as the distance H between the barrier and the pixel in the aforementioned first direction for the sake of using one parallax barrier. Also, the observation distance OD is preferably unchanged. Thus, the following Expression 35 is established.e′=e/3  (Expression 35)
This means that the pixel magnifying projection width is (e/3). As a result, in the same way as with a fly eye lens, a phenomenon occurs wherein regardless of the display device displaying a three-dimensional image, the observer cannot recognize the three-dimensional image.
Further, with a three-dimensional image display device equipped with a parallax barrier on the rear surface of the display panel, the same phenomenon occurs. In this case as well, the pixel pitch in the second direction is one-third in the first direction, and the aforementioned Expression 25 is substituted with the following Expression 36.e′=((OD+H)/H)×P/3  (Expression 36)
At this time, the distance H between the barrier and the display pixel should be the same value as the distance H between the barrier and the pixel in the aforementioned first direction for the sake of using one parallax barrier. Also, the observation distance OD is preferably unchanged. Thus, the following Expression 37 is established.e′=e/3  (Expression 37)
This means that the pixel magnifying projection width is (e/3), in the same way as with a fly eye lens, and a phenomenon occurs wherein, regardless of the display device displaying a three-dimensional image, the observer cannot recognize the three-dimensional image.